Method for applying antistatic agents to polymeric substances and destaticized articles thereby obtained



29, 1958 w. E. wALLl-:s 2,832,697

METHOD FOR APPLYING ANTISTATIC AGENTS TO POLYMERIC SUBSTANCES AND DESTATICIZED ARTICLES THEREBY OBTAINED Filed April 30, 1956 IN VEN TOR. W//e/m Wa//es a/Man,

ATTORNEYS United States Patent() "fi ce NIETHOD FOR APPLYING ANTISTATIC AGENTS TO POLYMERIC SUBSTANCES AND DESTATL CIZED ARTICLES THEREBY OBTAINED Wilhelm E. Walles, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Application April 30, 1956, Serial No. 581,554

Claims. (Cl. 117-69) polyethylenic molecular chain to which are attached various nonaromatic, substituent groups or radicals so `as to overcome their propensity for accumulating static electrical charges. It also has reference to the destaticized articles resulting from such application.

Various hydrophobic and essentially linear polymers andvcopolymers including those prepared from or containing polymerized quantities of such substances as vinyl chloride, vinylidene chloride, acrylonitri'le and the likefas well as such polymeric -substances Vas halogenated polyethylene and the like consist essentially of a saturated polyethylenic molecular chain to which various non-aromatic substituent groups and radicals are attached. "For convenience, such hydrophobic polymeric substancesfwill herein 'be referred to as substituted, non-aromatic hydro'- carbon polymers. Such terminology will be intended to bear especial reference to such hydrophobic and essentially linear polymeric substances as maylbe selected lfrom the group consisting of polymers and copolymers of vinyl chloride; polymers and copolymers of vinylidene Vchloride (including the several sarans); polymers and copolymers ot acrylonitrile; and chlorinated polyethylene. ,.It also comprehends such polymeric substances, exclusivev of polyethylene, as polypropylene, polybutylene and the like and substituted derivatives thereof.

Many of lthe hydrophobic, substituted, non-aromatic hydrocarbon polymers are possessed of attractive properties which make them desirable for employment'in various shaped -articles including ibers, filaments, yarns, threads (and fabrics constructed therefrom), ribbons,

tapes, foilsr'tilms, sheets, moldings and the like.. Shaped 2,832,69? Patented Apr. 29, 1958 articles ifrom-such polymericsubstances, h,cwever,.fexhibit an inordinate capacity for accumulating surface charges of static electricity. This characteristic makes them extremely diflicult and unwieldyto manipulate and handle during various manufacturing.operations `and 'use applications. It also lessens their attractiveness in other aspects yfor being employed for many purpose s.- For example, many individuals l,may objectfto the zdelitescent electrical -shocks they may-be subject to lor the sparks that-may be discharged when itheyrserve as the etfective grounding means for substituted,nonfaromatic, hydrocarbon polymer articles `when there is a considerable accumulation of electrical Icharges on the articles. iFun therxnore, electrostatically charged substituted, non-,aromatic, hydrocarbon polymer-articleszglisplaygreat tendencies :to collect dust and '.dirt and vto.have undesirably high degrees of soil retentivity. This, of course, limits their adaptability for being uti'lizedin a completely satisfactory manner for many upholstery, furnishing, decorative and other uses.

While it Vwould be highly advantageous ,to eliectively and in a substantially permanent Amanner provide antistatic agents and materials on the lsurfaces of substituted, nonaromatic, hydrocarbon polymer articles, great d-ifculty has |been encountered in achievingy such ka desideration, especially with antistatic agents of theY frequently employed type having both hydrophobic and hydrophilic group-s in .their molecules. The significant chemical inertness of most substituted, nonaromatic, hydrocarbon polymers andthe relatively smooth,sle.ek and impervious surfaces which occur kon the .vast majority of shaped articles from such polymeric materials usually prevent suitable chemical bonding or physical attachment, or both,'from being obtained with the antistatic agents that may be applied thereto. As a consequence, most antistatic agents and materials are not suliicientlyfsubstantive for or adherescent on substituted, non-aromatic, hydrocarbon polymerarticles to avoid having an undesirable susceptibility for |being teas-ily removed upon-exposure to various solvents, including `water and organic materials.

It is among the principal objects of the present invention to provide an improved method'for applying antistatic vagents containing bothhydrophobic and hydrophilic groups, in Itheir molecules -to.substituted, non-aromatic,:hydrocarbon polymer `articles `so that they-might ybe lessxpropenseto developstatic electric charges. It is alsosansobjectiof the inventionI to provide ai method for applying such antistaticagents fto substituted, non-arovanstrebt' y matic, hydrocarbon polymer articles so that thewageunts are effectively and substantially permanently retained on the articles despite rigorous exposure lto washing and cleaning with water and organic materials and other solvent exposures. An additional object is to provide a more eliicient method for utilizing antistatic agents so that -they may be applied in minimum amounts, significantly less =than the amounts conventionally required, for effective treatment. It is among .the ancillary objects of the invention -to provide destaticized substituted, non-aromatic, hydrocarbon polymer articles 4which result from practice of the method. It is a predominating object of the present invention to accomplish these intendments Without detraction from or deletion of the other desirable characteristics and properties `of such polymeric materials.

According to the present invention, all or any desired portion of the surface of a substituted, non-aromatic, hydrocarbon polymer or an article made therefrom may be destat-icized by a method which comprises subjecting the surface of the substituted, non-aromatic, hydrocarbon polymer or article to the action of a sulfonating reagent selected from the group consisting of concentrated sulfurie acid containing at least about 80 percent by weight of H2804; oleum which contains less than about 20 percent by weight of dissolved, free sulfur trioxide; anhydrous solutions containing oleum which contains less than about 20 percent by Weight of dissolved,` Yfreesulfur trioxide, and'free sulfur-trioxide; and subsequently applying to thethereby sulfonated surface an'antistatic lagen-t ythat has both hydrophobic and hydrophilic groups and contains a functional basic nitrogen atom in its molecule. More advantageously, thesulfonating reagent may be selected from the group consisting of concentrated sul furie acid containing at least about 96 percent by weight of sulfuric acid; oleum which contains less than about 4 percent by weigh-t of dissolved, free sulfur trioxide; anhydrous solutionscontainingfoleum which contains less than about -44 percent by weight of dissolved, free sulfur trioxide; and free sulfurtrioxide vapors. It may be desirable for freefsulfurgtrioxide vapors to be diluted to a concentration as low as l()4 percent or less, for example, witha suitable inert gas' such4 as nitrogen.

Advantageously, the sulfonated surface may be washed free from excess sulfonating reagent'prior to the application of the antistatic4 agent. Practice` of the method of the invention, if carefully conducted, has no adverse effect on pigments and otherfadditaments `such as-stabilizers and the like whichmay be Adispersed throughout the substituted, nonaromatic, hydrocarbon polymer for various purposes. After application of the antistatic agent, the destaticizedproductyr'nay` be employed satisfactorily in any application wherein it is 'desirable for it to be substantially free from surface accumulation of static electrical charges. The functionallybasic nitrogen atom-containing antistatic agent' is effectively and substantially permanently retained on destaticized substituted, non-aromatic, hydrocarbon ypolymer articles in accordance with the invention.

While the surface sulfonation of the substituted, nonaromatic, hydrocarbon polymer may beiaccomplished with any ofthe sulfonating agents of the invention, it is, as lhas been indicated, usually-'more advantageousv to employ sulfuric acid which contains at least about '96 percent by weight of H2804 vor an oleum (which sornetimes vis known as turning sulfuric acid) which contains from trace amounts to about 4 percentbyweightA of dissolved, free sulfur trioxide. 4Ifdesired, the oleum` can also be employed advantageously in anhydrous solutions or mixtures with other materials such ias acetic anhydride and the like which permit effective quantities ofthe sulfur trioxide tobe available in an amount-which 'isf equivalent Generally a satisfactory degree of surface sulfonation of the hydrophobic substituted, non-aromatic hydrocarbon polymer article may be obtained when operating at temperatures between the freezing point of the sulfonating reagent and about C. for periods of time ranging from matters of merely several seconds, or even almost instantaneous periods which involve mere fractions of seconds, to hours. Frequently, when sulfuric acid is employed which contains at least about 96 percent by weight of H2504 the treatment may be performed suitably at an operating temperature of about 50 C. within a time period of about ten minutes. When an oleum is employed which contains dissolved, free sulfur trioxide in amounts ranging from traces to about 4 percent by weight, the treatment may be performed suitably at an operating temperature of about 30 C. within a time period of about tive minutes.

The degree of surface sulfonation which is obtained on the substituted, non-aromatic, hydrocarbon polymer article predetermines the relative quantity of the antistatic yagent that may be effectively and permanently attached thereto upon its subsequent application and, for all practical purposes, precurses the results which may be realized by practice of the invention. The degree of sulfonation lthat may be obtained in any particular instance is somewhat interdependent on the nature of the substituted, non-aromatic, hydrocarbon polymer and the specific physical form or structure of the polyethylene article that is being treated, the strength or effective sulfur trioxide concentration of the reagent, the operating temperature and the length of the treatment. Care should be taken to avoid sulfonation conditions which may be too strong or vigorous, as may occur when an oleum is employed with a relatively high free sulfur trioxide content at too high ra temperature or for too long a period of time. *Care should also be taken to employ more moderate treating conditions upon more delicate structures such as fine filaments or fibers and the like. lf such precautions are .not asiduously observed, the substituted, non-aromatic, hydrocarbon polymer article may be caused to decompose and degrade resulting in its being darkened and discolored to an intolerable extent. Converselyyoptimum Vdestaticizing results may not be obtained if overly weak sulfonating conditions are employed which may not sufficiently modify the surface of ther substituted, non-aromatic, hydrocarbon polymer article to4 permita suitably benecial quantity of the antistaticagent to be effectively and permanently applied thereto. i

The functionally basic nitrogen.atom-containing antistatic agenthaving both, hydrophobic and hydrophilic groups in its molecule that may be employed in the prac- ,tice of` the invention may be a primary, secondary or tertiary amine type of material or it may be an amide or a material in which the functional nitrogen atom is contained in a heterogeneous ring system. Advantageously, :for example, it may be an aminepolyoxyalkylene type of material. A material of the type that is the condensed product of a long chain fattyacid amine containing from 8 to 16 carbon atoms in its molecule and a polyoxyethylene that contains an average of from 5 to 40 and, advantageously, in the neighborhood of 20 ethoxy groupsmay frequently be employed with especialjbeneii't. Such a material is a readily available product, being commercially obtainable, for example, from the Atlas Powder Company under the trade-designation G`37v80., l

Other functionally basic nitrogen atom-containing antistatic agents that may be employed advantageously inthe practice of the present invention include such commercially available materials and their lequivalents as are included in the following tabulation which sets forth a designation of what is believed to be `the general type vof'material involved` and includes their commercial tradenames or trade-designations and the names of the manufacturers fromwhom :they-have been available.

acacia? Type of antistatic Agent Trade-Name Manufacturer substituted oxazolines Fatty alkylolamine condensate Fatty alkylol amide condensate Fatty amine condensate Alkyl polyoxyethylene glycol amide Alkaterge A" Alkaterge E. Alkaterge T"-. Alkaterge C" Alromine RA" Alrosol B- uAlrosol 0".. "Alrosol H". "Alrosol 0" Alrosol 8.. "Alrosperse ll Antarox G-lOD".

Amide amino condensate Emkageu Concentrate;

Commercial Solvents Corporation.

'KGeigy Chemical Company.

Do. Autara Chemicals Division of General Aniline &'Film Aem-lah i al i pex em c ornpany. Drew & Co. E. F. Houghtondz'Comp'any. Dexter Chemical Company. Ciba Company. Pecks Products Company. Qiaker Chemical Products orp. E. F. Drew & Co.

. Do. Emulsol Chemical Corporation.

Emkay .Chemical Company.`

Cl "Emulsept" Eitiulsol Chemical Corporaon. CHdCHi)COOCHCHQNHCOCHiN Tertiary amines; ethylene oxide condensation Ethomeen" Armourvz Co.

products of primary fatty acids. Fatty acid condensate of N-methyl glucamine and "Glucaterge-IZ" Commercial Solvents Corpococonut fatty acids. ration. Fatty acid condensate of N-methyl glucarnine and "Glucaterge-28" Do.

cottonseed fatty acids. Modified lauroyl imidazolene hydroxy acetate "Miranol OH Miranol ChemicalY Company. Compounds formed by addition of propylene oxide "'letronics" Wyandotte Chemicals Corto ethylene diamine followed by addition of poration. ethylene oxide. substituted amide of alkyl phosphate H H RN P"ONHR Victor Chemical Company.

R CizHzs. R'=Water solubilizing group.

Victamine C4 Since the application of the antistatic agent on the sulfonated polymeric surface is essentially in the nature of a metathetical reaction, there is little criticality involved in the conditions of its employment with respect to time, temperature and concentration. It is usually beneficial and convenient, however, to apply it from a relatively low concentration dispersion or solution in a suitable liquid medium such as water. This manner of employment permits immersion of the sulfonated substituted, non-aromatic, hydrocarbon polymer in an applieating bath of the antistatic agent although, if desired, other applicating techniques may also be utilized for the antistatic agent. The extremely effective and substantially permanent retention of the antistatic agent by the substituted, non-aromatic, hydrocarbon polymer inthe practice of the invention is believed to be due to the combined bonding iniluence of the so-called Van der Waals forces to the surface of the hydrophobic portion (usually hydrocarbon in nature) of the antistatic agents molecule and the additional ionic attraction that is involved between the sulfonated surface and the functionally basic nitrogen atom-containing antistatic agent that is applied thereto. This permits an effective treatment to be accomplished with much smaller quantities of an antistatic agent, frequently in an amount which need only be 1A@ or less as much, in comparison to that which is conventionally required.

- Any Idesired degree of destaticization of the substituted, non-aromatic, hydrocarbon polymer article may be` effected. ',Generally, within the limits. of beneficial operating conditions, longer `and more intense sulfonations permit the subsequent applicationof greater amounts ofi the antistaticagent to yield products having greater de. grecs of antistatic characteristics. Itis. possible, Lfor example, to prepare a substituted, non-aromatic, hydro`` carbon'polymcr article that is sufficiently destaticizedv so as to be substantially completely antistatic incharacter.` Advantageously, the invention may be practiced with fabricated articles including fibers, filaments, yarns,` threads, ribbons, tapes, foils, lms, sheets, moldingsand. the like and on materials constructed therefrom such `asf cloth and fabric from textile iibers, filamentsand the; like of the substituted, non-aromatic, hydrocarbonpoly mer. As indicated, an entire surface need not be de` staticized on such fabricated articles as films.` and moldings or on other articles. If it is not desired or required t'oI obtain the benefit of a completely dest-aticizcdf surface.i only certain preferred areas or. portions of a surface may: be treated in accordance with the invention. f

In the accompanying drawing there is schematically illustrated a lamentin Figure l and a sheet in Figure as being typical substituted, non-aromatic, hydrocarbon' polymer articles whose surfaces may advantageously'be; destaticized in accordance with the present invention.A The following examples are given to further illustrate the invention.

Example vinylidene chloride in the'polymer molecule was `immersed in 100 percent concentrated sulfuric acid at a temperature of about 60 C. for about tive minutes. After being sulfonated, the film was washed thoroughly in water and then immersed in a l percent by weight aqueous solution of a fatty acid aminepolyoxyethylene condensate Y which theyhad been subjected. The nal results are as follows; v

. L h i t 47- IIA BII UCI' I A Resistance in meg-ohms more than 800 800 antistatic agent obtained from .Atlas Powder Company under the trade-designation G 3780 which was maintained at a temperature of about 50 C. The immersion was continued for about live minutes before the treated ilm was removed from the solution of the antistatic agent, washed thoroughly with water-and dried. Its surface resistivity, which is an indication of its antistatic properties, was then tested by tautly connecting a'sample of the destaticized iilm between two electrodes, each of which were 7 centimeters long, spaced parallel 4 centimeters apart and across which there was applied a 500 volt direct current potential. The test lwas conducted at room temperature under about 80 percent relative humidity. The surface resistivity of the destaticized film was found to be between about 10S-109 ohm-centimeters. .In cornparison, untreated film of the same'type has a surface conductivity between about 1012-109 ohm-centimeters. As is generally understood, a surface which is relatively more electrically conductive or` less resistive is usually more antistatic in nature in that it tends less to-accumulate charges of static electricity. t

Example II Sample u A MB1 CH Resistance ln megohms more than 100,000 100, 000

YAll of the samples were then immersed for five minutes in a 1 percent by weight aqueous solution of G 3780 antistatic agent at 50 C., after which they were washed in cold water for live muates. Their surface resistivity was then measured and, as indicated in the following tabulation, they were all found to have become destaticized, although the effect was much less pronounced in Sample A:

sample Au Bn non Resistance in meguhms 2, 000, 000 80o Each of the samples was then washed in water for about V2 hour at 55 C. Upon additional testing, Sarnple A was found to have lost its antistatic characterstics, as evidenced by a return to its original resistance value. This is shown below:

Sample Au MB1: Cn

Resistance in megohms more than 800 800 s, 000, 000

The three samples were then washed for live minutes in acetone and retested electrically. No detectable change in the antistatic characteristics of the destaticized samples were obtained, despite the severelyk extractive exposures to Similar excellent results may bel obtained when other sulfonating conditions within the scope of the invention are employed on articles comprised of polymers of vinyl chloride; articles comprised-of copolymers of vinylidene chloride and vinyl chloride; and articles comprised of chlorinated polyethylene containing from about 2 to 60 percent by weight of lsubstituted chlorine in the polymer molecule and when other, antistatic agents containing functional basic nitrogen atoms, particularly amine-polyoxyalkylene type materials, are utilized.

It'is to be -fully understood that the present invention is to be construed Vancl interpreted not by the foregoing didactic description and specification but in the light of what is set forth and defined in the appended claims.

What is claimed is:

l. Method for destaticizing hydrophobic, substituted, non-aromatic'hydrocarbon polymers and articles made therefrom comprised of substantially linear polymers and copolymers consisting essentially of the polyethylenic molecular chain to which are attached non-aromatic substituents which comprises subjecting the surface of the polymer to a sulfonating reagent which is selected from the group consisting of concentrated sulfuric acid containing at least about80 percent by weight of H2504;

.oleum which.'A contains less than about 20 percent by weight-of dissolved, free sulfur trioxide; anhydrous solutions containing oleum which contains less than about 20 percent by weight of dissolved, free sulfur tn'oxide; and free sulfur trioxide; and subsequently applying to the sulfonated surface an antistatic agent that has both hydrophobic and hydrophilic groups and contains a functional Ybasic nitrogen atom in its molecule.

2. The method of claim l wherein the article is comprised of polymeric substances selected from the group consisting of polymers and copolymers of vinyl chloride; polymers and copolymers of vinylidene chloride; polymers and Acopolymers of acrylonitrile; and chlorinated polyethylene.

v3. kThe method of claiml wherein the reagent is comprised ofvconcentrated sulfuric acid containing at least about 96 percent by weight of H2804.

4. The method of claim l wherein the reagent is comprised of oleum which contains between trace amounts and about 4 percent by weight of dissolved, free sulfur trioxide.

5. The method of claim l wherein the article is subjected to the sulfonating reagent at a temperature between the freezing point of the reagent and about C.

6. The method of claim l and including the steps of washing the sulfonated article free from the sulfonating reagent before applying the antistatic agent; washing the article after application of the antistatic agent; and drying the destaticized article.

7. The method of claim 1 wherein the functionally basic nitrogen atom in the antistatic agent is contained in a heterogeneous ring system in the antistatic agents molecule.

8. The method of claim 1 wherein the antistatic agent is an amine-polyoxyalkene type of material.

9. The method of claim 1 wherein the antistatic agent is a fatty acid amine-polyoxyalkylene type of material.

l0. The method of claim l wherein the antistatic agent is the condensed product of a long chain fatty acid amine containing from 8 to 16 carbon atoms in its molecule and a polyoxyethylene that contains an average of from 5 to 40 ethoxy groups.

- l1. A destaticized, solid, hydrophobic, substituted,

hydrocarbon polymer comprised of substantially linear polymers and copolymers consisting essentially of the polyethylenic molecular chain to which are attached non-aromatic substituents said polymer having a sulfonated surface to which is applied and bonded an antistatic agent that has both hydrophobic and hydrophilic groups and contains a functional basic nitrogen atom in its molecule.

12. The destaticized polymer of claim 1l comprised of a polymeric substance selected from the group consisting of polymers and copolymers of vinyl chloride; polymers and copolymers of vinylidene chloride; polymers and copolymers of acrylonitrile; and chlorinated polyethylene.

13. The destaticized polymer of claim 11 comprised of a copolymer of vinylidene chloride that contains a. major proportion of vinylidene chloride polymerized in the copolymer molecule.

14. The destaticized polymer of claim 1l wherein the functionally basic nitrogen atom in the antistatic agent is contained in a heterogeneous ring system in the antistatic agents molecule.

15. The destaticized polymer of claim 11 wherein the antistatic agent is an amine-polyoxyalkylene type of material.

16. The destaticized polymer of claim 11 wherein the l0 antistatic agent is a fatty acid amine-polyoxyalkylene type of material.

17. The destaticized polymer of claim 11 wherein the antistatic agent is the condensed product of a long chain fatty acid amine containing from 8 to 16 carbon atoms in its molecule and a polyoxyethylene that contains an average of from 5 to 40 ethoxy groups.

18. A shaped polymeric article in accordance with claim 11.

19. A polymeric lrn in accordance with claim 11. 20. A polymeric flamentary article in accordance with claim 11.

References Cited in the file of this patent UNITED STATES PATENTS Re. 23,062 Horton Sept. 20, 1955 2,255,940 Rogers Sept. 16, 1941 2,400,720 Staudinger May 21, 1946 2,576,980 Treue Dec. 4, 1951 2,626,876 Carnes Jan. 27, 1953 2,727,831 Dixon Dec. 20, 1955 OTHER REFERENCES Vojulskii et al.: Doklag Akad. Nak. S. S. S. R. 73; 

1. METHOD FOR DESTATICIZING HYDROPHOBIC, SUBSTITUTED, NON-AROMATIC HYDROCARBON POLYMERS AND ARTICLES MADE THEREFROM COMPRISED OF SUBSTANTIALLY LINEAR POLYMERS AND COPOLYMERS CONSISTING ESSENTIALLY OF THE POLYETHYLENIC MOLECULAR CHAIN TO WHICH ARE ATTACHED NON-AROMATIC SUBSTITUENTS WHICH COMPRISES SUBJECTING THE SURFACE OF THE POLYMER TO A SULFONATING REAGENT WHICH IS SELECTED FROM THE GROUP CONSISTING OF CONCENTRATED SULFURIC ACID CONTAINING AT LEAST ABOUT 80 PERCENT BY WEIGHT OF H2SO4, OLEUM WHICH CONTAINS LESS THAN ABOUT 20 PERCENT BY WEIGHT OF DISSOLVED, FREE SULFUR TRIOXIDE, ANHYDROUS SOLUTIONS CONTAINING OLEUM WHICH CONTAINS LESS THAN ABOUT 20 PECENT BY WEIGHT OF DISSOLVED, FREE SULFUR TRIOXIDE, AND FREE SULFUR TRIOXIDE, AND SUBSEQUENTLY APPLYING TO THE SULFONATED SURFACE AN ANTISTATIC AGENT THAT HAS BOTH HYDROPHOBIC AND HYDROPHILIC GROUPS AND CONTAINS A FUNCTIONAL BASIC NITROGEN ATOM IN ITS MOLECULE. 